Height issue in 3d mesh in Cloud

PIX4Dcloud PIX4Dcloud Questions/Troubleshooting
1

Hi Folks

 

I’m trying to share my point cloud and 3d mesh from a project I have processed on desktop. The project was processed with GCPs in terms of our local coordinate system (Poverty Bay 2000) which is available in pix4d. 

I have uploaded the project files (without processing) and then uploaded the point cloud .las and mesh .Obj and can view them in the 3d window.

The issue is the heights for the 3d mesh are incorrect and are different to the desktop mesh. The cloud .las has come in correctly.

It looks like the textured mesh has been converted to WGS84 so maybe that is the issue?

2

Hi Tim. The cloud only supports WGS84 currently so that is why the change in project CS. We are looking into displaying in the project CS declared in the p4d file and local project so that may be improved in the future. Could the difference in values be that the units of measurement are not the same? i.e the cloud reporting meters and the local project in feet? 

How significant are the differences in hights? can you send examples and screenshots?

3

Hi Holden The units for the height datum is in metres, it is a local datum that approximates mean sea level.

 

Below are two images showing heights and coordinates of the same point in the cloud data and the 3d mesh.

The 3d mesh is around 27m lower than the cloud data. The cloud data heights are correct. The mesh horizontal coordinates are way off too

 

 

 

 

 

 

 

4

It looks like this is due to the fact that the mesh and pointcloud are actually vertically offset in the model. You can confirm this by displaying both simultaneously, one is loaded above the other. Im not aware of any other reports of this happening. I would try reprocessing the dataset to see if the problem remains after.  

5

Hello,

Any update on the project CS being displayed? This is definitely a must for sharing these results.

Thanks.

6

Hi,

At the moment, the results are still displayed in WGS 84 (lat/long/alt) on the Pix4D Cloud. However, we have added your vote on this.

Best,
Teodora

7

Hi

I think I am having this same issue.

The outputs I require and that our clients are familiar with is a local coordinate system IG75 (Irish Grid).

Processing, display and review of the models in Mapper (and converted to IG75) works fine but upon upload to the cloud, the XYZ in the 3d Mesh model are way off. Any DSM, Orothomosacis and Point Cloud models display correctly.

Is this the same issue as has been discussed in this tread. Referring back along the thread and to jan 19 comment from Holden_Greene “The cloud only supports WGS84 currently”, does that mean that everything uploaded should be projected in WGS84 as this has not been my experience. Only the 3d Mesh is causing an issue?

If this is the same issue and relates to the Mesh only, can you confirm or estimate when a fix for this will be available?

8

Hi @brianpburns101

The reply from Holden is an old post dated January 2019. Pix4Dcloud now supports different coordinate systems.

The issue you are facing is due to the merged viewer/editor that displays the non-georeferenced 3D mesh and the georeferenced point cloud together. Indeed, if you upload the mesh ( .obj, .jpg and .mtl ) as a result to the Cloud, it won’t be georeferenced. However, there is an option to align the uploaded mesh with the point cloud.

If you upload the .obj, .jpg, .mtl files together with the offset .xyz file (you can find this last one in the \1_initial\params folder) in the 3D Mesh box, the uploaded mesh will be properly aligned with your point cloud and the 3D model will appear. It is important that all the 4 files are uploaded at the same time or at least the offset file is uploaded first and the 3 files for the mesh are uploaded later, so I suggest that you copy the offset.xyz file in the 3d_mesh folder and then drag and drop them in the 3d mesh box of the Files > Results view for uploading.

9

Thanks Alice.

That worked